Aetna CEO: Obamacare In A 'Death Spiral' Heading Into 2018. Aetna and Humana have called off their deal amid government concerns over competition. Here's a look back at six pivotal moments that led to this. Aetna and Humana have called off their deal amid government concerns over competition.
For the plant genus, see Synapsis (plant). Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis.
Synaptic vesicle exocytosis occurs in neurons of the nervous system. Neurons communicate through electrical or chemical (neurotransmitters) messages that are exchanged at synaptic junctions between nerve cells. Synaptic vesicles are formed by endocytosis of the plasma membrane at pre-synaptic nerve terminals.